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Kinase activity associated with caldesmon is Ca2+/calmodulin-dependent kinase II
G C Scott-Woo1, C Sutherland, M P Walsh
1Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, Alberta, Canada.
The Biochemical Journal
|June 1, 1990
Summary
Researchers investigated a kinase interacting with caldesmon, finding its properties closely match Ca2+/calmodulin-dependent protein kinase II (CaM-kinase II). This suggests the kinase is likely a smooth-muscle isoenzyme of CaM-kinase II.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Caldesmon is a calmodulin-binding protein involved in cytoskeletal regulation.
- Ca2+/calmodulin-dependent protein kinase II (CaM-kinase II) plays crucial roles in cellular signaling.
- Identifying specific kinase-substrate interactions is key to understanding cellular processes.
Purpose of the Study:
- To determine the identity of a kinase that co-purifies with caldesmon.
- To compare the properties of this kinase with known CaM-kinase II isoenzymes.
- To investigate its role in the phosphorylation of synapsin I.
Main Methods:
- Studying the phosphorylation of bovine brain synapsin I, a known CaM-kinase II substrate.
- Assessing the kinase's substrate specificity, kinetics (Km), and response to Ca2+ and calmodulin.
- Analyzing the effect of pre-phosphorylation of the kinase on synapsin I phosphorylation.
Main Results:
- The co-purifying kinase efficiently phosphorylates synapsin I (Km = 90 nM) at two distinct sites.
- Synapsin I phosphorylation by this kinase is dependent on Ca2+ and calmodulin.
- Pre-phosphorylation of the kinase enhances subsequent synapsin I phosphorylation, bypassing the need for Ca2+/calmodulin.
Conclusions:
- The investigated kinase exhibits properties highly similar to CaM-kinase II.
- The findings strongly suggest that this kinase is a smooth-muscle isoenzyme of CaM-kinase II.
- This identification advances the understanding of kinase function in cellular signaling pathways.